In the fabrication of ink jet devices, passageways are provided to connect an ink supply, such as a reservoir, to nozzle outlets in the print head. These passageways can be made at the edge of a die, or through holes in a bottom surface of the die. Feeding ink from a bottom of the device can use valuable space in the device and feeding ink from the edge can require an architecturally complicated device.
An example of a typical fluidic micro-electromechanical system (MEMS) print head device 100 is illustrated in FIGS. 1A and 1B at sequential stages of assembly. In particular, FIG. 1A illustrates a silicon wafer 110 supporting a transducer 112 and a bond pad 114. A fluid chamber 160 is formed on the silicon wafer 110 by a nozzle plate 130 distanced from the silicon wafer 110 with generalized support member 150. At least one nozzle opening 140 is formed in the nozzle plate 130 and at least one fluid inlet 120 is formed in the silicon wafer 110. In FIG. 1B, the device of FIG. 1A is shown placed onto a print head substrate 170, wirebonded 116, and sealed with encapsulant 190 at ends of the silicon wafer 110, print head substrate 170, and nozzle plate 130 junctions. An aperture 180 is formed in the print head substrate 170.
In known fabrication of semiconductor devices of the type described above, when the device of FIG. 1A is placed on the print head substrate 170, alignment of the ink inlet 120 with the aperture 180 of the print head substrate 170 can be problematic to achieve. Further, the area of the ink inlet 180 can be about 100×200 μm to facilitate deep reactive ion etching through the silicon wafer 110. In addition to consuming valuable space on the silicon wafer, reactive ion etching is an expensive process. For example, a per wafer etch time on the order of about five hours can be needed to form a 500 to 600 μm deep ink inlet. In addition to the time required for forming the ink inlet, an overall area of the silicon wafer must be large enough to accommodate formation of the ink inlet as well as allow for alignment tolerances, resulting in about a 20% margin at the edge of the silicon wafer. Typically, this margin is used for support member 150 of the nozzle plate 130.
The amount of silicon and surface area required for forming a fluid interconnect is typically defined by a combination of the ink inlet 120 and margin. In a typical MEMS ink jet device, the die can be about 2000 μm wide. If the total overhead of the ink inlet represents 200 μm, for example, a potential 10% reduction in usable space of the die results. On a 150 mm wafer, a 2 mm×12 mm die size yields 563 die. If the die width is reduced, for example, by 10% (1.8 mm), a yield of 624 die per wafer can be obtained. Accordingly, the die yield can be directly proportional to a reduction in the size of the cut die. This can become particularly important for architectures having large array designs where both die size and array size are important fabrication considerations.
Thus, there is a need to overcome these and other problems of the prior art and to provide a method for forming an ink feed structure in an inkjet print head, which reduces a size of die used in the method and resulting device.